Methods of manufacturing evacuated and gas-filled devices



April 26, 1960 METHODS QF MANUFACTURING EVACUATED AND GAS-FILLED DEVICES Filed Dec. 28. 1956 V. J. DE SANTIS ET AL 2 Sheets-Sheet 1 April 26, 1960 v. J. DE sANTls -v:afg-A1. 2,934,392

METHODS DE MANUFACTURING EVACUATED AND GAS-FILLED DEVICES Filed Dec. 2a, 1956 2 sheets-sheerz ROBERT E. MANFREDI,

TEMPERATURE IN C.

THORIUM TITANIUM zlRcoNluM loV 20o so 46o 56o so 16o so 96o looo noo lzoo TANTALUM FIG. 2.

seo

METHODSV on MANUFAcTUniNG nvAcUATE AND GAS-FILLED DEVICES f Y Vincent il; De Santis,Robert E. Manfrednand" Henry J.

arent" Nolte, SchenectadyyNX., assignors to General Elec- Y tric Company, a corporation of New York Application December 28, 1956, Serial No."631,321V` 16 claims. (c1. sir-' z's) The present invention relates generally to` evacuated and gas-filled devices and pertainsvmore particularlyv to new and improved methods of manufacturing same.

In various arts such, for example, as the electric discharge device, electric switch, electric lamp, and vacuuminsulated container arts, devices are often manufactured which are eitherY evacuated of their gaseous contents to a high degreelor are evacuated of the normal atmosphere A' and subsequently' charged or iilled to a predetermined degree witha particular atmosphere. Heretofore, the

evacuation required for both types of devices generally hasl been accomplished by mechanically exhausting or pumping down-thegaseous contents thereof. In accordanceV with'some prio'rart methods the required degree of exhaust has been obtained solely by the utilization of mechanical exhaust equipment which for the present discussion is considered to include pumps of the oil sealed and vapor-diffusion types.Y With other methods, and par-V ticularly in the electric discharge device and lamp arts, the devices have been first mechanically exhaustedand then undesirable residual. gases have been chemically sorbed by means ofthe well-known gettering processes.

Most of these Vmethodsinvolve.the necessity of mechanical exhaust equipment, therprovision of exhaust tubulations or vacuum connections on the devices,and require the step of pinching-olf or sealing' suchutubulations following exhaust and in a manner which will'not adversely affect ,the4 previously attained vacuum. From the stand- Additionally, in the variousarts mentioned, and4 par- `ticularly theelectric discharge device art, it is generally the practice to bake-out, vor evolvethrough heating, and to exhaust gases ordinarily occluded in the materials of the components ofthe devices, in order that such gases cannot subsequently deleteriously alfec't a vacuum or gas charge obtained therein.

Furthermore, often suchdefvices `are manufactured to include cathode structures comprising materials which, in order to be rendered active for emission, must be chemically reduced. This Vis generally accomplished by energizing the cathodes substantially above normal operating temperatures following the aforementioned bake-out step.

A heating step is also'often required to complete ythe envelope structure of the device, as by brazing together the various parts comprising'the structure, such for example, as insulative wall sections and metallic terminal members. ,Y

From the preceding discussion it will be appreciated that the ordinary processing of devices-generally involves a vplurality of separate heating steps to accomplish bakei A, 2,934,392 Patented Api. 26,1960

ice

out, cathodeactivation andV sealing, and such procedure has been found both costly `and time consuming.

u As regards the manufacture of gas-filled .devices which previously have been evacuated in preparation for receiving ga-s charges, such, for example, as hydrogen thyratons or inert-gas discharge tubes or switches, there is generally encountered a problem in avoiding admission of undesirable gases during charging. Additionally, in manufacturing some gas-filled devices, there is often encountered the further problem of maintaining the lilling within a desired pressure range required for normal, prolonged, efficient operation. Thus, it is desirable to provide means and methods for facilitating the charging of gas-iilled devices as well as maintaining the filling at desired operating pressures during the normal life of the device.

Accordingly, the primary object of the present invention is to provide new and improved methods of manufacturing evacuated e devices. p

Another object'of the present invention is to provide a new and improved method of evolving occluded gases from an envelope andits contents and sealing and evacuating the envelope by means of a single heating step and without any heretofore-required exhaust tubulation or mechanical exhaust equipment.

.Another object of the present invention is to provide a new' and improved hydrogen furnace process whereby an envelope structure comprising multiple parts may be brazed, sealed and permanently evacuated to a high d egree. p

Another object of the present invention is to provide a new and improved method of manufacturing an electric discharge device` wherebywchemical,constituents thereof requiring reduction to be eifective may be reduced in conjunction with the evacuation of the devicey and as a result of a singleheating step. e ,f Y U Y v Another objectof the` present inventionA is to provide newA and improved methods of gas `charging an envelope.

e Still another object of the present invention is to provide7`new and improvedqmethods nof manufacturing evacu- :ated and gas-filled devices whereby substantial economies in `rnanufacturing effort, time and materials and improved quality are realized. g y, v i

Further objects and advantagesof the present invention will become apparentas `the following description, proceeds `and the features ofnovelty which characterize the invention will be pointed out with particularity in the claims annexed'to and forming part of the specification.

In carrying out the objects of the present invention Vanfen'velope is heated to a predetermined elevated temperature range in an open condition in a predetermined atmosphere whereby the `normal gaseous contents of the envelope are substantially displaced by a thermally expanded quantity of the predetermined atmosphere. Heated in the envolep while it is open is a quantity ofesubstance capable of sorbing a substantial quantity of the predetermined atmosphere in the predetermined elevated temperature range and at relatively reduced temperatures. The envelope is sealed while in the mentioned predetermined elevated range and then the envelope and its contents are permitted `to cool.' Thus, the internal pressure of the envelope can bev effectively reduced. The envelope can comprise multiple parts adapted 4for being joined as by brazing to complete the envelope and the envelope can be adapted for being sealed thermally; and both -thebrazing and sealing can comprise the same step and can be elfected by the same heating step as that utilized to raise the temperature of the gas-sorbing material in theenvelope. Thus, brazing, sealing and evacuation can Vbeelected in a single step, resulting in a substantial' reduction in manufacturing expense and time.' Additionally, the same heating stepcan be utilized apagan its contents, and can be further employed to reduce chemically any of the material in the enveloped device thatfrequires reductions for desired operation. For a better understanding of the invention reference may be had to the accompanying drawing in which:

Figure 1 is a schematic illustration showing both a device constructed in accordance with an embodiment of the invention, and processing equipment that may be utilized in carrying out the method of the present invention;

Figure 2 is an enlarged fragmentary perspective illustration of a portion of an enveloped device sealed and evacuated in accordance with the method of the present invention, and with the equipment illustrated in Fig. l.

Figure 3 is a charge illustrative of the effects of some of the materials, quantities thereof and operating temperatures employed in the method of the present invention; and

Figure 4 s an enlarged sectional illustration of `an enveloped device sealed and charged with hydrogen in accordance with a modified form of the present invention.

Referring to Figure l, there is shown a furnace, generally designated 1, of a type in which the method of the present invention may be advantageously carried out. The furnace 1 is elongated and comprises apre-heat zone 2, an intermediate zone 3 and a cool-down zone 4. The zone 3 is adapted for being directly and concentratedly heated as by a suitably'arranged and adjustably controllable electrical heating arrangement generally designated 5. The opposite ends of the furnace comprisingV the pre-heat and cool-down zones are heated indirectly by the arrangement 5. The end walls of the furnace may comprise access doors 6, provided for permitting Athe placing of objects to be processed into the pre-heat zone 2 and removing same from the cool-down zone 4.

Provided on the floor orIbottom wall of the furnace is a pair of spaced rails 10 on which objects can be moved through the furnace.l Movement of the objects on the rails and through the various zones of the furnace mayA be effected by operation of a push rod generally designated 11, slideably arranged in and operable through the access door 6 in the right-hand side of the furance in Figure 1. 'It will be understood that any suitablel conveying means can be employed, such for example, as a chain drive, for moving objects through the furnace.

Gas'inlets 12, including means for selectively adjusting the gas flow therethrough, are provided in the wall of the furnace on either side of the heating arrangement and an outlet 13 is provided in the lower portion of each of the doors 6. Except for the mentioned inlets and outlets, the furnace is adapted for being closed during operation.

For purposes of explanation the present invention is illustrated and hereinafter will be described principally with reference to the manufacture of electric discharge devices. This is desirable inasmuch as evacuated electric discharge devices generally require a high degree of evacuation and removal of substantially all active gases in order to avoid contamination of the usual electrode elements contained in these devices. Thus, the evacuation capabilities of the present invention will be more strikingly presented. Also, gas-filled electric discharge devices represents a good example of the types of `enveloped devices that can be gas charged by means of the present invention. However, from the outset it is to be under- Y A 4V for being bonded together, as by brazing or soldering, to provide an` electric discharge device" hereinafter generally designated and comprising an envelope 16, an anode 17, acathode structure 18 and a grid structure 19.

The'anode 17 can comprise the planar bottom portion of a cup-like member 20. The member 20 is adapted for comprising the upper end of the envelope 15 and isv provided witha rim 21 formed with a downturned lip 22. The lip 22 is adapted for surrounding and being bonded, as by brazing, to the outer peripheral surface of the upper end of a high-refractory insulative sleeve 23 adapted for comprising part of the side wall of the envelope 16. 'Ihe sleeve 23 may be formed of any suitable ceramic material such, for example, as alumina or magnesium silicate and. may be metallized in the brazing areas according to the method disclosed in United States Letters Patent 2,667,432, issued January 26, 1954 to Henry I. Nolte anda-assigned to the same assignee as "i the present invention.

stood that the invention is not limited in application to Y electric discharge devices but is applicable to the manuheat zone V2 of the furnace and on the rails v10 therein is a stacked arrangement of elements which are adapted Seated between. the rim 21 of the Vanode member 20 and the upper end of the sleeve 23 Vand adapted for veffecting a metallic bond therebetween `in a manner to be described in Vdetail hereinafter is a Washer 24 formed of any suitable solder` material. Associated with the lower end of the yinsulative sleeve 23 and reentrant in the sleeve 23 is a substantially frusto-conical conductive 'grid-support member 2S. As 'illustrated in Figures 1 and`2, the aforementioned grid structure 1,9 vmay comprise a planar array of grid wires 26 supported `in a substantially parallel spaced relation to. the anode .17 on vthe inner end of the support member 25 extending into the sleeve 23. As best illustrated in Figure 2 the support member 25 is formed to include a n'm 2'7 having an upturned lip 2S adapted for surrounding and being bonded, as by brazing, tothe upper peripheral surface of the lower end of the sleeve 23. Seated between the riml 27 and the lower end of the sleeve 23 is a solder washer identical in construction and purpose to the washer 24. These and other identical washers will hereinafter be referred to simplyas washers'` 24.

Provided for being bonded tothe lower side of the rim 27 of the grid support member is a conductive sealing ring 30 including a downturnedlip 31 adapted for surrounding and being bonded, as bfy-bralzingV also, to the outer peripheral surface of an upper end of asecond 4insulative sleeve 32. The sleeve`32 can be formedv of the same material as the sleeve 23. and is also adapted for comprising part'of the side wall of the envelope le..

vformed with radial corrugations, providing a plurality of substantially large passages affording communication between the interior and exterior'of the envelope 16. Bcfore brazing occurs the envelope assembly is open in the sense that gas can pass into and out yof the assembly at all the solder washers and between the various sections of the assembly. However, it will be seen that the washer 33y is effective for holding the upper and lower sections of the envelope structure apart a lsubstantial amount and thus affords v greater gas flow between the sections of the envelope. The washer 33 is effective in this manner until the washer melts, andthe purpose for providing such communicatonwill be brought out in .detail hereinafter.

Associated with the lower end of the `sleeve A32 is a tubular conductive cathode-support member 34. '[ne cathode-support member 34 is similar to the grid-support member 25 and is formed with a rim 35 having an upv-ated temperature.

@tailed example appearing hereinafter. regards the effects of the material ofthe disc 50, the term fr l'imfs.- -ilduihe 1110.?!@13 @BdfL-Qf file.; Slee@ lznlsfrQneori-e .abovermemioned-f solder tweakers f2.4- .sA-gnduf-ivessaling-.ring .37. dentigalfto. .the-.allg 3:0- and including. a dawn- .turned lip 38, is lprovided for being brazedfto the -r-im-` 35 of the 1. .cathode ...Support .member 1.314. throughitthe .use gf, a --washerfof the .type-includinathe radial. .corrusatonsand designated .33 `in Figure; 2 Thens .S7-.is .adapted also i-for being brazed kto the upper end of-a-third ceramic sleeve 40 through the use of a washerM-24. The sleeve ...40 can. be .identical t0. the .Sleevegl The cathode-supportfmember 35 includes a substantialtj-lyfrusto-conical `conductive portion reentrantV inthe sleeve 32 and having-,the cathode` structure 1.8., suitably,

conductively mounted thereon. The cathode structure .-18

,can comprise a container orvsleeve-42supporting1an electronemissive disk ,43v in Vpredetern'lined spaced relation -lyvith'the wires ofthegrid 1,9. The disledcan be lformed of the conventionalcarbonate materials adapted'forfbeing emissive following activation ,or reduction thereof to oxides upon heating to a predetermined substantially ele- A lamentary heater .44 is contained vin `the sleeve andv one side thereofcan be .suitably electricallyfconnected to the cathode-support member A34. VvProvided at the lower end of thesleeve 40 is a conductive,

`inverted, cup-like member 45 adapted forY closing the .lower end of the envelope 16. The member 4Sis1formed A.with a rim 46 and anupturned lip. portion` 47, and a Ywasher 24 is provided between therim 46 andthe lower .end of the sleeve 40.for effecting a brazetherebetween. irThemember 45 has the other` .end .of -tliertl-amentary theater 44 suitably electricallyconnected thereto.

As willbev clear from the drawing, the lip portions of the various electrodesupport elements 'and sealing rings -..are adaptedfor-serving as external electrical contact` surtzfaces on the device and, accordingly, these members-can ".beadvantageously formed of copper or clad-chrome iron.

.'1-Brovided in the envelope .16 in the form of a disc 5t) and adaptedfor use in effecting evacuation of the envelope -by sorption, in a manner to be described in detail here- .:inafter,is a predetermined quantity of elemental titanium.

VThe yquanti-ty of the titanium used is dependentupon the internal volume of the envelope 16, temperature employed and .other factors which will be understood -from a de- Additionally,- as

fsorption will hereinafter be employed to refer genericalv:ly to the .phenomena o-f-.absorptionand adsorption and the term desorption willbe used `in reference tothe reverse processes. .The disc 50-is supported on .the internal surface of the member 4S and, `in orderv to avoid undesirable alloying of thetitaniumwith the material of-'the member 45` an interposed layer of molybdenum 51 is provided. This ...arrangemenh is also adapted for facilitating detection lof leaks in a manner to be described hereinafter. As yshown in the drawing, titanium 50 and the molyb denum layer 51 maybe centrally apertured, thus to provide for direct connection of one of the heater leads to the member 45.

Following stacking ofthe-various elements comprising the device in the manner described above and illustrated in Figure l, the stacked arrangement is placed in the pre-heat zone 2 of the furnace 1. The furnace 1 is continuously supplied through the inlets 12 with dry hydrogen and the excess furnace atmosphere is perl mitted to escape from the furnace through the outlets 13 in the ends of the furnace. The supply of hydrogen and escape thereof is such that the atmosphere of'the furnace is continuously being replenished by dry hydrogen and any other gases in the furnace are flushed out through the outlets 13. Additionally, in the furnace the hydrogen is heated and thereby substantially -expanded or-rareed. The advantage of thiswill be brought out in detail hereinafter.

In the pre-heat zone Zithe cathodedisc 43 can be .i6 Lactivated, or chemically Areduced from carbonates to oxides, by. completing a circuit through .the iilamentary heater-44 anda powersource generally indicatedat 52. A pair of electricall contacts-,53 are provided in the fur- ,5 nace structure to facilitate contact with the cathode terminals comprising the upturned lips 36 of the `cathodesupport -member 34and the rim 46 of the member 4 5. 1nthisfmanner the .cathode filament or heater can.be ,energized sufficiently to reduce the carbonate material 10, of the disc 43 Vforpthus rendering the disc satisfactorily.

emrnissive at contemplated normal operating temperatures.

Also, while the device `15 is in the pre-heat zone 2 itfisheatedsufficiently to commence a bake-out opera- 15 ltion or the evolution ofundesirable occludedgases in VVthe material of the device, such for example as oxygen, water vapor, nitrogen, carbondioxideand carbon mon- .;OXld- The devie 15 is Ytransported onthe rails 10 tothe 20 heating-zone 3.asby manipulation of the pusher 11,

and fthe heatingarrangement 5 is energized to elevate :the temperature of ,the device substantially, thus to complete the bakefoutlstep. Normally the material Aof thedisc-Sil includes an oxide coating resulting fromex- .25.. posure to the normal atmosphere. During elevation of the temperature of the-deviceinthe heating zone this .coating is disposed of, after which the titanium first sorbs .hydrogen and thendesorbs substantially allthe hydrogen .it-had previously sorbed. 6 The desorbed hydrogen .ex-

.pands outwardlyof the-device throughI the communica- `tive'A openings-Vor passages. between the 4interior. and ex- .-.terior.. of Vthe envelopeE afforded by .the corrugationsgof fthewashers- 33 as well, asspacesbetween theenvelope .sections andJthesOIder-,Washers 24 until thereoccurs ..35a substantial.e1ullibriumof pressure betweenthe. at-

Av.rnospherein the device and that `in the-furnace. .Ardditionally, the passages afforded by the ,washers enable the atmosphere .of the furnaceand the gaseous contents fof the device, including the `normal atmospheric constituents, the residualgasesresulting from activation of the cathode and out-gassing of the materials of the device, to admix. Due to the above-described continuous replenishment of the Vdry hydrogen atmosphere in the furnace and the llushingeifect afforded thereby, the ladmixing. of the gaseous: contents ofthe envelope and furnace atmosphere results in such gaseouscontents of the-envelope being iiushed out and substantiallydisplaced bylan essentially pure hydrogen ,atmosphere c orresponding to the expanded or rareed atmosphere of the furnace. "At a predetermined elevated temperature the solder washers 24and 33 flow, thus to sealhthedevice and e entrapping in the envelope a residual quantity of the V- mentioned expandedorrareed essentially pureA hydro- --gen atmosphere.

.55 -lt-will be understood from the foregoing that the pres- -ent invention is not limited to the use of the corrugated --washers 33-to provide substantial,communicative 'pas- `sages between the interiorandexterior of the envelope structure or, invother words, to hold the envelopeopen to a degree which will facilitate the flushing step. Various alternative methods can be employed. -FDL example, a-mechanical fixture operable from the exterior` of the furnace can be employed for gripping-one4 ormore kofthe' sections of theenvelope and holding samein a .35 raised position relative-to an adjacent lower sectionfcarsorbing substantial quantities of hydrogen atirelatively low temperatures and releasing or desorbing hydrogen fat elevated temperatures, or in other words, the titanium reacts reversibly with hydrogen. This phenomenon is explained in detail in chapter Q of vthe text entitled, Vacuum Techniques, written by Saul Dushman and published by John Wiley and Sons.

Additionally, at the elevated temperatures at which the titanium 50 releases hydrogen, it is further'etfective for Virreversibly sorbing vorreactingwith active gases other than hydrogen. TheV compounds thus formed with these other active gases Y are stable and, therefore, there'is no disassociation when the material assumes relatively low temperatures.

Where it is desired to use corrugated solder washers to hold the envelope open these washers, as well as all other solder washers, are formed preferably of a solder material that will flow and seal or close the envelope of the device in a'temperature range in whichvthe titanium the temperature is reduced toward the lower side of the range in which the sealing occurs substantially all of the active gases other than hydrogen rrwill have already been sorbed by the titanium and only the residual hydrogen and any residual inert gases will remain in the device. Additionally, atthis stage of theprocess the titanium is in almost its pure elemental state and the previous heating thereof has effected a lattice change in the structure of the material which makes it more solvent or more highly sorbing of the residual hydrogen upon cooling. Thus, the next step of the process involves reducing the temperature of the device, including the titanium therein, as by rst transporting the device into the cool-down zone 4 of the furnace and vthen removing it completely from the furnace. In this manner, the solder material is solidified to form the seals 54 shown in the left-hand side of Figure l. Additionally, as the Itemperature of the device, and therefore, the titanium disc 50 decreases, the titanium voraciously sorbs the residual hydrogen or reacts therewith to form a subtitanium hydride, or a solid solution of hydrogen in titanium, and thus the device is evacuated substantially to a high degree. Any residual inert gases are ordinarily in small and negligible quantities such, for example, as below -10 mg. of mercury and for most practical purposes are not found deleterious to operation of the evacuated device.Y

Inasmuch as titanium hydride is a granular substance and is generally undesirable in an uncontained form in a device such as 15, the member 50 is formed of sufficient material to insure that it will not be completely converted to titanium hydride upon sorption of the entrapped hydrogen. That is, after the member 50 has served its purpose in evacuating the device, it will normally comprise a uniform solid solution of hydrogen in titanium and will still constitute, a unitary element. Additionally, the member 50, after serving to evacuate the device, is adapted for serving as what might be termed as a built-in leak detector. That is, if any of the seals 54 is defective leakage into the device of atmospheric hydrogen will ultimately convert the member 50 to granular titanium hydride which upon shaking of the device, will cause a rattling noise, signifying a leak.

The final pressure obtained in the sealed device can be viewed as a function of the internal volume of the device, the amount of material used in forming the member 50, and the operating temperature of the device inasmuch as temperature increases will tend to release previously sorbed hydrogen from the member 50; The critical or minimum amount of material to be used in the member 50 for obtaining a vacuum inthe device 'apagada can be defined as the stoichiometric equivalent of the quantity of gases in the tube at the time of sealing. However in order to insure a desired high vacuum, to avoid conversion of the material Ito anfundesirable granular state, and to minimize operating-'temperature effects on the internal pressure of .the device, it has been found desirable to form the member 50 of a quantity of material approximately Itwo to three times theamount considered to be critical.

The member 50 is located remote yfrom the cathode in the device in order to avoid-any substantial heating of the member 50 during normal operation of the tube which would have the tendency of releasing previously sorbed hydrogen.v

In order .that the just-described process may be more readily practiced a detailed example including quantities, temperature ranges and -times forperforming the various steps of the process is provided herebelow:

Example A In an enveloped device of the -type designated 15 in the drawing and having an internal volume of approximately 69 cc., the titanium disc 50 can beformed of approximately 148 mg. of titanium. Additionally, the solder comprising the washers 24 and 33 can be silver solder adapted for melting and flowing into the joints between the-various elements at approximately 778 C. which, as seen-in Figure 3, is beyond the inflection point on the titanium curve. Alternatively and in place of the corrugated solder washer a flat solder washer can be used in conjunction with any suitable means adapted for holding a section of the envelope in a raised position and Voperable for lowering the raised section onto the molten solder thereby to seal orv close the envelope at approxiand other gases being released in the envelope.

kmately 778 C. The furnace 1 is heated by means of the arrangement 3 and is supplied with dry hydrogen. The device 15 is placed initially in the pre-heat zone Z wherein flushing out or displacement of the normal gaseous contents thereof by the hydrogen atmosphere of the furnace commences. Additionally in the pre-heat zone of the furnace the cathode 43 is activated by completing the circuit of the larnentary heater 44 through the power source 52 and thus raising the temperature of the cathode to approximately'1000" C. This temperature is maintained preferable for approximately l2 minutes. Thus, the carbonates of which the cathode material is formed are reduced to oxides and rendered p artially active or emissive. This reduction and activation step also results in carbon-monoxide, carbon-dioxide These gases are also flushed out of Vthe envelope or displaced vby the continuously replenished hydrogen atmosphere of the furnace.

the device is constructed heats up and evolves occluded gases, thus'to commence the out-gassing of the'process. The gases thus evolved are also flushed out by the hydrogen.

Subsequently, the device is transported on the rails 10, as by operation of the pusher 11, into the heating Zone 3. In this zone, and by continuous energization of the furnace heating arrangement 5, the temperature of thev device and its constituent parts is raised and maintained for approximately 10 minutes in a range between approximately 778 C. and 1000 C. In approaching this temperature range the oxide coating normally present on the titanium is decomposed and the titanium first sorbs hydrogen from the hydrogen atmosphere now vpresent; in the envelope, which sorption generally occurs -its"r`eve'rsible reactive nature in respect to hydrogen. In

the mentioned range, substantially all of the hydrogen previously'sorbed by the titanium is released and subvvhydrogen from the furnace atmosphere.

frtatltiallyfall of :thefgasesenormaliyt oceludedfinthemay,terials'offthedevice lare `,halted-out anddisplaced by Additionally 1n this range, after approximately 2. or 3 minutes therein, thesolder material melts, the washers 33 collapse and .the envelope is thereby sealed. The resultant seals remain in a molten state but are effective for entrapping in the envelope an essentially `hydrogen atmosphere. Still ifurther, in the mentioned range, and throughout the remaining time therein, the titanium is effective for permanently or irreversibly combining with any active gases in ithe envelope, other than hydrogen, which had not been .displaced by hydrogen fromthe furnace atmosphere or which were evolved from the materials of the device subsequent to sealing of the envelope. -It is to be recognized that the bake-out process continues as long as the device is maintained in the elevated temperature range and the f titanium will continue to be etective in sorbing evolved gases lfor an extended period even after; sealing of thedevlce occurs, or inl other words for as longas the bake-out results in evolution of gases and as long as the titanium stands at a temperature whereat it will combine with such drogen in the device. The 148 mg. of titanium is pref- -f erably more than is required to sorbA all the hydrogen in an enveloped device having thevolume of the device V15. Thus, upon cooling to room temperature the titanium sorbs all of the hydrogen and without converting completely to a granular hydride, leaving the device evacuated to a ,high degree.

Byfollowing the steps of the method described-5in Example A, it has been possible toconstruct electrical `discharge devices evacuatedto pressuresin the order of magnitude ofl 1 10.-'7 mm. Hgand having normal electrical operating characteristics. Of coursethe lamount of titanium used is also proportional to the internal volume vof the device evacuated .and thefamount of titanium employed may be increased orfdecreasedjin accordance as the internal volume ofthe device isirr is tusedfirii place. of titanium the method'of thefpresent invention may be practiced as follows:

.Example B lIn an enveloped device such as 15 of the drawing `and having the same approximate internal volume of Y69 cc. the d1sk50 can be for-med of approximately 282 mg. of zircomurn, which is the atomic weight equivalent of 148 mg. of titanium. Thereafter the device 15 can be `processed through the hydrogen furnace in the same manner described above with regard to Example A Wherein titanium was employed, except that preferably the washers 24 and 33 are formed of a higher-melting-point solder so that sealing of the device will occur at a higher temperature and beyond the inilection point on the Vzirconium curve, as illustrated in Figure 3. For example,

the washers`24 and 33 can be formed of a solder adapted for flowing in a temperature range of approximately 1000 C. .and 1l50 C.,and solidifying at approximately 1000 C. Thus, following activation of the cathode in the pre-heat zone 2 of the furnace in the above-described mannerY and following a period of heating in the pre-heat zone to initiate bakeout, the device can be moved into the heating zone 2i wherein it is elevated in temperature, by suitable energization of the heating arrangement 5 vto the above-mentioned range of approximately 1000 C.

to 1150" C. Commencing from Ithe time the device is creased or decreased, respectively, and in accordance with the degree of evacuation desired.

It will be understood from `the foregoing and figure '3 of the drawing, that the present invention is not limited -to the use of titanium. TitaniumV has been described inV the detailed example given above in view `of the v-fact that its use has not been found objectionable in. electric discharge devices, where it is importantthat-,no substance be introduced into the device which would have adverse effects onfthe electrodes therein and thusA on the electrical operation-.of the. device. It `-will be further understood that titanium hydride is equally employable in the present methodinasmuch as it will, upon heating, be reduced to titanium and hydrogen, which resultant titanium will operate in the same mannerV that described above. Of course, titanium hydride is granular and for some applications it will be necessary or `desirous to provide some form of gas-permeable containing means. therefor.

. Zirconium is another material which upon heating re-' acts reversibly with hydrogenhand irreversibly with other the method of the present invention is` appliedztowthe .evacuation of electricdischarge devices- Wlaere ziranium.,

rst placed in the furnace the hydrogen atmosphere of fthe furnace operates toward completely flushing out or displacing the original Vgaseous contents of t-he device as well as other gases resulting from cathode activation and bake-out. When `the above-mentioned temperature is attained the washer material becomes molten to effect sealing of the envelope and entrapment there/in of a substantially pure hydrogen atmosphere.

If it is desired to employ means other than the corrugated washers to hold the envelope widely open during the hydrogen-ilushing. step of the process, such other means can be arranged to effect closure or sealing of the envelope at the same temperature at which the corrugations of the solder washer would collapse to effect sealing.

rDuring heatingv of the device to the above-mentioned temperature` range, first, the normal oxide coating of the zirconium will decompose and the elemental zirconium will commence` sorbing hydrogen from the furnace atmosphere. Thereafter and at a higher temperature this reaction will reverse and the zirconium Will desorb hydrogen leaving the zirconium in a lattice condition conducive to substantial and ready sorption of or combination with active gases, other than hydrogen, at elevated temperatures and with hydrogen upon a subsequent decrease in temperature.

The device is held at the mentioned temperature range -for approximately ten minutes during which the abovementioned out-gassing continues and the zirconium continuously and'irreversibly reacts or combines with any evolved active gases other than hydrogen in the device. t Following the `ten minute heating period the device is and entrapment therein of the above-mentioned rareiied hydrogen atmosphere.

Subsequently the device is removedv completely from the furnace Vand the zirconium cools through a range wherein it reacts substantially with, and thus sorbs, the

`residual hydrogen, thereby to effect a high degree of evacuation of the device. This method of obtaining a vacuum is facilitated by the fact1thatthe hydrogen which was heated and therefore substantially expanded or rareed when sealed or entrapped in the device is, relatively small in quantity at the reducedtemperaturefandihe above-.mentioned further fast that the previsrvsihseing i of the zirconium has left it in a lattice condition highly conducive to gas sorption.

It will be understood that in this example also the amount of zirconium employed is4 proportional to the internal volume of the device to be evacuated and that it may be varied proportionally in accordance with variations in volume of the device. It will be yfurther Aunderstood from the foregoing and Figure 3, that if desirable a suitably contained quantity of zirconium hydride can be employed in place of a member of elemental zirconium.

Additionally, while the step of cathode activation has been described above as effected by energization of the cathode heater, it is to be understood that, if desired, cathode activation can be effected by means of the same furnace heating step that is employed to melt the solder, etc. When activation is accomplished in this manner it is generally desirable to use a'higher-melting solder.

' It will be understood from'the foregoing that the described hydrogen-furnace is not limited to the use of titanium" and zirconium and the hydridesI thereof nor to the evacuation of electric discharge devices. Instead, this method broadly contemplates a method of highly evacuating and sealing in a single operation any enveloped device or container and the use in such method of any material or alloy of materials selected from the group of materials which are reversibly reactive with hydrogen and are highly sorbing of hydrogen at reduced temperatures. This group not only includes titanium and. zirconium and the hydrides thereof but, as shown in Figure 3, also includes cerium, thorium, vanadium and tantalum and the hydrides of each of these elements. Further included in this group, but having no representative curves on the chart ldescribed process and has been effective forreacting 4with the various active gases over a wider temperature range and at higher rates of gas sorption than generally obtainable with either titanium or zirconium alone. Additionally, instead of alloying these materials,'individua1 quantities thereof can be used combinationally.

A quantity of any one of the above-mentioned materials having an atmoic weight equivalent of the 148 mg. of titanium mentioned in Example A will be operative in the present method for evacuating any enveloped device having an internal volume Yof approximately 69 cc.; and, of course, this quantity can be varied proportionately in accordance with variations'in size of the device.

f Each of the above-grouped materials hask different characteristics and is either more or less suited for use in evacuating particular enveloped devices or containers in accordance with the method of the present invention. For example, these materials react with hydrogen and the various other active gaseous elements at diiferent temperatures and rates. Thus, some of these hydride-forming materials are more desirable than others for use with particular solder materialsand where the duration of the heating step is necessarily or desirably limited. Ad-

ditionally, even though such materials are all reversibly reactive with hydrogenand adapted for substantial hyl drogen sorption at reduced temperatures and, thus,k

adapted for use in the present invention as broadly contemplated, for given amounts some materials are more sorbing. Thus, some materials are more desirable from thestandpoint of economy in space, which is a major factor in the evacuation of small volume devices, such.'

- as sub-miniature electron tubes, and thelike, and from the further standpoint of economy -in cost, which in respect to some material can be considerable Where production is high. Further, some of the mentioned materials, including palladium, react reversibly with hydrogen, but do not react irreversibly or at a satisfactory rate with other active gases. These materials, while they may not be suitably adapted for evacuation of electric discharge devices or any other devices which require substantially high degrees of evacuation of all active gases, are satisfactory for the evacuation of other devices such as, for example, vacuum bottles or insulation panels which require a substantially high degree of evacuation but which are not substantially adversely affected by small residual quantities of active gases. Still further, some of the above-noted materials are currently less feasible cornmercially from the standpoints of costs and availability even though theoretically they lare as equally suitable in carrying out the presently disclosed process as others.

Thus, it will be seen from the foregoing that the material to be selected from the above-noted group for the purpose of practicing the hydrogen furnace method of the present invention will be dependent largely on such factors, for example, as the type of device to be evacuated by means ofthe present method, the other materials used in the device and the -size of such device as well as the temperatures and solder materials desired to be used and the commercial availability and cost of the selected material.

It will be further understood from the foregoing that while dry hydrogen has been found particularly suitable as the furnace atmosphere in evacuating electric disi charge devices in the manner described above primarily owing to the fact that the activated oxide cathode would be adversely affected by moisture, the described method, broadly considered, requires only that the atmosphere y. supplied to the' furnace be essentially hydrogen.- That is,

for the evacuation of some devices the described method may be practiced employing, for example, forming gas which is a commercially available gaseous admixture comprising approximately 8% to 20% nitrogen and the remainder hydrogen by volume. Of course, when using Vthese gases itis necessary to select from the above-noted group a material which will react satisfactorily with both vci) the hydrogen and elements comprising the other gaseous constituents and it is necessary to utilize a suicient quantity of the material to sorb all of the elements required to be sorbed for satisfactory operation of the device. Additionally, it is necessary to select a sealing temperature at which the hydrogen-sorbing material will be best adapted for reacting with the gases entrapped in the device.

.It will be appreciated from the foregoing that for the evacuation of some types of devices, such as those not adversely affected by the presence therein of oxygen, water vapor, or the like during processing, the method of the present invention can be practiced with the use of other than hydrogen or essentially hydrogen atmospheres.

As pointed out above, titanium, zirconium and the other above-mentioned materials are capable of reacting irreversibly with most active gases other than hydrogen. Thus, a device 15 including the above-described thermally operative sealing means or brazing material and a quantity of titanium, zirconium, etc. will, when heated, in an atmosphere, for example, of nitrogen, air, carbon monoxide, or carbon dioxide, rst evolve occluded gases from the various materials of the device, then become illed with an expanded quantityor portion of the particular gas used, and then become sealed by the melting of the brazing material, thereby to entrap the mentioned expanded portion of gas. Both before and after sealing the gassorbing substance contained in the device will be effective for sorbing the activegases in the device, the active gases other than hydrogen beingirreversibly sorbecl at the elevated temperatures, and the-hydrogen, if any, being screw L assesses 'i3 sorbecl when the device subsequently cools. v"lfhusfthe device is both sealed and evacuated by one heatingV step; and Where the envelope of the device is formed by conjoining component parts, the sealing and conjoining are accomplished by one and the same brazing operation, and are effected during the same heating step that renders the gas-sorbing material reactive with the entrapped gas. lInasmuch as the entrapped gas is thermally expandedjn effect, less gas is required to be sorbed than otherwise.

In order to eiect the desired evacuation it is necessary to provide a suicient quantity of titanium or other gas-sorbing material. This quantity can be equal to the molar equivalent of the quantity .of gas to be sorbed.

`It is further necessary to control thebrazing time to prevent saturation of theV gas-sorbing material by the gas of the atmosphere before sealing which would render the material ineective for sorbing e gas and evacuating the device after sealing. This can be accomplished by rapidly heating the device yand the gas-sorbing material to the desired elevated temperature.

When carbon dioxide is used as the furnace atmosphere barium oxide can be employed as the `gas-sorbing material instead of the above-mentioned materials. The barium oxide will, at relatively low temperatures, react reversibly with the carbon dioxide to form barium carbonate and at higher temperatures will form carbon vdioxide and barium oxide. Thus, when the above-described com- `bined brazing, sealing and evacuating process is practiced using barium oxide as the gas-absorbing material it will give up carbon dioxide at the elevated temperature at which outgassing and brazing occur, and after sealing the material will sorb entrapped carbon dioxide, thereby to `evacuate the device.

It will be further see nfrom the foregoing that the present invention could be carried out in the normal at` mosphere, if the proposed uses of a device whose internal pressure has been reduced in this manner will tolerate the inal pressures obtainable. That is, if the invention is practiced in the normal atmosphere it is possible to `elect sealing, brazing together of component envelope -parts and heat-cycling of the gas-sorbing material necessary to render it effective for sorbing the 'gas entrapped l after sealing, all by means of a single heating step. However, because of the amounts of noble gases normally present in the atmosphere and which will not be sorbed,=\

thev final pressure in the device will be less than, for exi ample, where a dry hydrogen latmosphere is utilized to sweep out the noble and other gases.

It will be still further understood from the foregoing Vthat "while the method of the present invention has been phere a predetermined amount of the desired inert gas.

Thus, when the device is sealed in the furnace it contains a quantity of inert gas along with an entrapped portion of the furnace atmosphere. Following sealing, the titanium, or other appropriate material selected from the above-mentioned group, effectively sorbs or combines with the gases in the device other than the inert gas in the manner described above, thus leaving the device evacuated of all the gases other than the inert gas or, in other words, illed or charged with the inert gas.

The degree of charging with the inert gas, is, of course, readily determinable or controllable by controlling the relative rates of inert gas and essentially-hydrogen gas admitted into the furnace and the sealing temperature. Alternatively, and, if desirable, the inert gas and essentially hydrogen gas can be admixed in predetermined vquantities externally of the furnace-and then fed thereinto. a

:The method of the Vpresent invention is valso applicable in obtaining a` hydrogen-filled or charged device such, for example, as a hydrogen thyratron. When the method is used for this purpose it is practiced in substantially the same manner described above with `regard tothe evacuation of enveloped devices, except that the quantity of titanium or other material used is not such as tosorb al1 the residual hydrogen following sorption of the other active gases and upon cooling of the device. Instead, an amount of material is employed which will sorb hydrogen vupon cooling only to the extent of bringing the pressure thereof down to a predetermined desired final or operating pressure. This amount of gas-sorbing material is determined preferably experimentally in connection with the particular tube structure and its contents because of varying conditions and tube materials andthe effects thereof on gas clean-up, surface sorption and solubility of the gas in the Velectrodes of the device.

The present invention also contemplates amethod and structure for maintaining the `abovementioned predetermined desired operating pressure during the life of a hydrogen-charged device.

A structure adapted for accomplishing this is illustrated `in Figure 4. This structure is similar to that shown in Figure l and identical numerals designate elements ywhich are identical in construction and purpose to those provided in the device of Figure 1. The device iof Figure 4 diiers from that of Figure l in that itcom- `prises an envelope 56 including an additional ceramic section 57 and conductive frusto-conical support member 58. The support member 58 is provided with a rim59`and an upturned lip portion 66 adapted for engaging the lower peripheral surface of the ceramic section 57 andV being `sealed thereto and to the other adjacent elements of the envelope structurein the same manner as that described above with respect to the device of Figure l.

The member 58 is re-entrant in the sleeve 57 and carries on the upper internal surface thereof one of the afor`ementioned disks 50 formed of a material selected from the above-noted group of materials characterized by their proclivity to sorb substantial quantities of hydrogen j at reduced temperatures. Alloying of the material of the member S0 to the supporting surface of the member `58 is avoided by an interposed layer of molybdenunrS'l.

:disk 5t) sorbs hydrogen in the manner described above. Subsequently, during the normal operating Vlife of the tube there is a tendency for the internal pressure of the Adevice to decrease. `When this occurs the internal pressure can be increased by energizing the heating element 60 which raises the temperature of the disk 5t), thereby to .desorb hydrogen therefrom for replenishing the charge of the device. It will be seen that the amount of hydrogen thus released from the disk can be controlled by controlling the energization of the heater 60.

While'we have shown and described specific embodiments of our invention we do not desire our invention to be limited to the particular form shown and' described and we intend by the appended claims to cover all modi- `cations within the spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:v

` 1. The method of sealing and evacuating an envelope comprising the steps of providing an envelope lwith an opening, disposing a thermally operative `sealing means in said opening, placing said envelope in an Aenclosure, supplying a predetermined active gas to. said enclosure substantially to displace the normal atmosphere in said atmosphere.

ofsaid envelope, heating said envelopetoy alpredetermined temperature range wherein said sealing means is rendered effective -for sealing said envelope and entrapping therein a thermally expanded portion of said gas, and including in said envelope a quantity of substance capable of sorbing a substantial quantity of the entrapped portion of said gas both while in said predetermined temperature range and upon subsequent cooling. v

2. The method of sealing and evacuating an envelope comprising the steps of providing an envelope with an opening, disposing a thermally operative sealing means in said opening, displacing the normal gaseous contents of said envelope with a thermally expanded quantity of a predetermined active gas, including in said envelope a quantity of a substance which is capable of desorbing said gas upon heating and sorbing said gas upon cooling, elevating the temperature of said substance and said l rareed quantity of said atmosphere, heating said subsealing means for effecting desorption of substantially all v previouslyso-rbed gas from said substance and then rendering said thermally operative sealing means effective for sealing said envelope to entrap a quantity of said gas therein, and permitting said substance to cool for effecting sorption thereby of the gas entrapped in Vsaid envelope. Y

3, The method of manufacturing an envelope having predetermined internal pressure conditions comprising-the steps of substantially displacing the normal gaseous contents of said envelope with -a heated and thereby substantially rariiied atmosphere comprising essentially hydrogen, including in said envelope a quantity of hydrogen-sorbing material which is reversibly reactionable with hydrogen, elevating the temperature of said material to desorb substantially all previously'sorbed hydrogen While said envelope is open, sealing said envelope and thereby entrapping a quantity of said rariiied atmosphere therein while the temperature of said material is elevated, and

permitting said material to cool for effecting sorption thereby of a predetermined quantity of the hydrogen entrapped in said envelope.

4. The method of manufacturing an envelope having predetermined internal pressure conditions comprising the steps of including in said envelope a predetermined quantity of material which is reversibly reactionable with hydrogen and irreversibly reactionable with other active gases, heating said envelope including said material while said envelope is open to an essentially hydrogen atmosphere and to a predetermined elevated temperature range wherein substantially all previously sorbed hydrogen is desorbed by said material and other active gases in said envelope are sorbed by lsaid material, sealing said envelope while in said predetermined elevated temperature range, whereby a substantially rarified quantity vof hydrogen is entrapped in said envelope, and cooling said material for effecting sorption thereby of a predetermined quantity of the hydrogen entrapped in said envelope.

5. The method of evacuating an envelope comprising Y the steps of including in said envelope a quantity of subst ance comprising material selected from the group including titanium, zirconium, cerium, thorium, hafnium, lanthanum, neodymium, praseodymium, vanadium, tantalum, columbium, palladium and the hydrides thereof, heating said envelope and its contents including said substance for evolving gases therefrom, displacing the gaseous contents of said envelope with an atmosphere comprising essentially hydrogen, sealing said Aatmosphere in said envelope, and reducing the temperature of said substance for effecting sorption thereby of the hydrogen heating said envelope opened in a ushing atmosphere stance to a predetermined temperature range wherein substantially all hydrogen is desorbed by said material and said material is adapted for sorbing active gases in said envelope other than hydrogen, sealing said envelope in said temperature range, and reducing the temperature of said substance for eiecting sorption thereby of the hydrogen sealed in said envelope.

7. The method of fabricating and evacuating an envelope comprising the steps of providing a structure including a plurality of members adapted for being joined to form a sealed envelope, including in said structure a quantity of substance comprising material selected from the group including titanium, zirconium, cerium, thorium, hafnium, lanthanum, neodymiurn, praseodymium, vanadium, tantalum, columbium, palladium and the hydrides thereof, providing a thermally operable bonding material between said members, substantially displacing the gaseous contents of said structure with an essentially .hydrogen atmosphere, heating said structure and substance for rendering said bonding material eiective to join said members and thereby complete a sealed envelope and for adapting said substance to sorb the residual hydrogen upon cooling, thereby to evacuate said envelope, and cooling said structure and substance.

8. The method of sealing and evacuating an envelope comprising the steps of providing an envelope with an open-ing, including in said envelope a quantity of substance comprising material selected from the group including titanium, zirconium, cerium, thorium, Vhafnium, lanthanum, neodyrnium, praseodyrnium, vanadium, tantalum, columbiurn and the hydrides thereof, disposing in Said `opening a brazing material adapted for flowing in a predetermined temperature range wherein said substance is adapted for desorbing substantially all previous- 1y sorbed hydrogen and sorbing active gases other than by said Vbrazing material is solidified and said substance cluding titanium, zirconium,cerium, thorium, hafnium,

lanthanurn, neodymium, praseodymium, vanadium, tantalum, columbium and thehydrides thereof, disposing in said opening a Abrazing material adapted for flowing in a predetermined temperature vrange wherein said substance is adapted for sorbing active gases other than hydrogen, heating said envelope and its contents to said predetermined range in a continuously refreshed dry hydrogenatmosphereywhereby gases are evolved therefrom, the gaseous contents of said envelope are substantially replaced'by a rareed essentially hydrogen atmosphere, active gases in said envelope other than hydrogen are sorbed by saidsubstanceand said brazing material is caused to liow for sealing said envelope, and

Areducing said temperature, `whereby said brazing material is solidified and said substance is rendered effective for `sorbing substantially all thel hydrogen sealed in said envelope.

10. Themethod of manufacturing an electric .discharge device comprising the steps of mounting inan open envelope an electrode assembly including a cathode comprising `material requiring activation, including in said -jenveope a substance comprising material selected from nu W l..

the group including titanium, zirconium, and the hydrides thereof and at least suicient in quantity for sorbing a quantity of hydrogen corresponding generally to the volume of said envelope, heating the material of said cathode to elect activation-thereof, substantially displacing the gaseous contents of said envelope with an essentially hydrogen atmosphere, heating said substance to a temperature range wherein it releases previously sorbed hydrogen and sorbs active gases in said envelope other than hydrogen, sealing said envelope in said temperature range, and cooling said substance for sorbing the hydrogen sealed in said envelope, thereby to evacuate said device. e

1l. The method of manufacturing an electric discharge device comprising the steps of mounting in an open envelope an electrode assembly including a cathode requiring chemical reduction for activation, including in said envelope a substance comprising materials selected from the group including titanium, zirconium and the hydrides thereof and at least suicient in quantity for sorbing a quantity of hydrogen corresponding generally to the volume of said envelope, chemically reducing said cathode, heating said envelope and its contents in an essentially hydrogen atmosphere, thereby to evolve gases therefrom and replace the gaseous contents of said envelope with a rareed quantity of said hydrogen atmosphere, heating said substance to a predetermined temperature range wherein said substance releases any previously sorbed hydrogen and sorbs residual active gases in said envelope other than hydrogen, sealing said envelope in said predetermined temperature range, and cooling said substance for sorbing the hydrogen sealed in said envelope, thereby -to evacuate said device.

12. The method of manufacturing an electric discharge device comprising the steps of providing a structure including a plurality of insulative and conductive members adapted for being joined by brazing to form a sealed envelope, providing brazing material between said members, mounting in said structure an electrode assembly including a cathode comprising materials requiring chemical reduction for activation, including in said structure a quantity of substance comprising material selected from the group including titanium, zirconium and the hydrides thereof and at least suicient in quantity for sorbing a quantity of hydrogen corresponding generally to the volume of said structure, chemically reducing said cathode, heating said structure and its contents in a dry hydrogen atmosphere, thereby to evolve gases therefrom and replace the gaseous contents of said structure with a rareiied quantity of said hydrogen, heating said structure and substance to a predetermined temperature range wherein said brazing material is caused to ow for joining said members to eiect a sealed envelope and wherein said substance releases any previously sorbed hydrogen and sorbs residual active gases in said envelope other than hydrogen, and cooling said substance for sorbing the hydrogen sealed in said envelope, thereby to evacuate said device.

13. The method of manufacturing an inert gas charged enveloped device comprising the steps of including in said device a quantity of substance comprising materials selected from the group including titanium, zirconium, cerium, thorium, hafnium, lanthanum, neodymium, praseodymium, vanadium, tantalum, columbium, palladium and the hydrides thereof, substantially displacing the gaseous contents of said device with an atmosphere comprising essentially hydrogen and an inert gas, sealing said atmosphere in said device, and heating said substance for eifecting sorption upon cooling of said hydrogen, thereby to leave said device charged with said inert gas.

14. The method of manufacturing an inert gas charged enveloped device comprising the steps of including in said device a quantity of material selected from the group including titanium, zirconium, cerium, thorium, hafnium, lanthanum, neodymium, praseodymium, vanadium, tantalum, columbium, and the hydrides thereof, `heating said device opened in a dry hydrogen atmosphere containing a predetermined quantity of an inert gas, thereby to evolve gases from the materials of said device and to eiect displacement of the gaseous contents thereof with an amtosphere comprising essentially hydrogen and said inert gas, heating saidv substance to a predetermined temperature range wherein active gases in saidV device other than hydrogen are sorbed by said substance, sealing said device, and reducing the temperature of said substance for eiecting sorption thereby of the hydrogen sealed in said device and thus leaving said device charged with a predetermined quantity of said inert gas.

15. The method of manufacturing a hydrogen charged envelope and determining the internal pressure thereof comprising the steps of including in said envelope a quantity of substance selected from the group including titanium, zirconium, cerium, thorium, hafnium, lanthanum, neodymium, praseodymium, vanadium, tantalum, columbium, palladium and the hydrides thereof and suicient in quantity to sorb a quantity of hydrogen less than the volume of said envelope, heating said envelope open in a hydrogen atmosphere, thereby substantially to displace the gaseous contents of said envelope with a hydrogen atmosphere, said heating adapting said substance for effecting sorption thereby upon cooling of only a predetermined quantity of said hydrogen for thus leaving said envelope hydrogen charged to a predetermined degree, and subsequently reheating said substance to a predetermined extent for increasing the hydrogen charge in said envelope.

16. The method of manufacturingV an envelope `having predetermined internal pressurev conditions comprising the steps of includingin said envelope a predetermined quantity of a substance comprising approximately 50 percent each of titanium and zirconium, susbtantially displacing the gaseous contents of said envelope with an atmosphere comprising essentially hydrogen, and heating said substance for electing sorption thereby upon cooling of -a predetermined quantity of said hydrogen over a substantial temperature range.

References Cited in the le of this patent UNITED STATES PATENTS 2,277,691 Curwen Mar. 31, 1942 2,334,718 Lowry Nov. 23, 1943 2,449,838 Brett Sept. 21, 1948 2,692,959 Wright Oct. 26, 1954 2,792,271 Beggs May 14, 1957 2,838,708 Yoder June 10, 1958 2,882,116 Williams Apr. 14, 1959 

